Control circuit for collision operated fire preventing and extinguishing systems



March 5, 1957 R. G. TOWLE ETAL 2,784,356

CONTROL CIRCUIT FOR COLLISION OPERATED FIRE PREVENTING AND EXTINGUISHING SYSTEMS 3 Sheets-Sheet 1 Filed June 12, 1953 M m w w V70. 1 m w H m 8 fr W Z w? March 5, 1957 Filed June 12, 1953 R. G. TOWLE ETAL CONTROL CIRCUIT FOR COLLISION OPERATED FIRE PREVENTING AND EXTINGUISHING SYSTEMS 3 Sheets-Sheet 2 IN V EN TOR.

3 Sheets-Sheet 3 R. G. TOWLE ET AL. CUIT FOR COLLISION OPERATED FIRE.

PREVENTING AND EXTINGUISHING SYSTEMS 6 m2 m ma 0 W m IG'F a f e n w 5. B

CONTROL CIR March 5, 1957 Filed June 12, 1953 United States Patent CONTROL CIRCUIT FOR COLLISION OPERA'ELD ggfis PREVENTING AND EXTINGUISHING SYS- Robert G. Towle, New City, and Arthur W. Uhl, IliWZlLii, N. Y., assignors to Specialties Development Corporation, Belleville, N. J., a corporation of New Jersey Application June 12, 1953, Serial No. 361,352 5 Claims. (Cl. 317-135) The present invention relates to fire preventing and extinguishing systems for aircraft and the like, and, more particularly, to a control circuit for operating such systerns in response to particular conditions occurring upon crash or collision of the craft.

When an airplane is involved in a collision, either in the air or in crashing to the ground, one of the greatest dangers is that its fuel and oil storage tanks and lines are broken and that the contents thereof are spilled and ignited and/or fuel vapors are caused to explode. Consequently, it has been proposed to fight such fires by installing fire extinguishing systems, fuel and oil shutoff valves and circuit breakers which are operated by a device responsive to collision or crash generally known as an impact or inertia switch.

Accordingly, an object of the present invention is to provide an improved fire preventing and extinguishing system of the foregoing type which is operable by a plurality of devices each responsive to a particular condition occurring upon crash or collision of the craft.

Another object is to provide such a system which is operable by these devices only upon the occurrence of at least two particular conditions.

Another object is to provide a control circuit for such systems which is safeguarded against false alarm opera tion.

Another object is to provide such a circuit which controls the necessary operations practically instantaneously and is disconnected from its source of electrical energy in a fraction of a second, whereby electrical sparking tending to ignite combustible fuel mixtures is prevented.

A further object is to provide such a circuit which can also be controlled manually and/or by fire detecting devices.

A still further object is to accomplish the foregoing in a relatively simple, practical and economical manner.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art .upon employment of the invention in practice.

In accordance with the invention, the foregoing objects are generally accomplished by a fire preventing and extinguishing system wherein a circuit is provided which comprises a source of electrical energy, electroresponsive means operable by the source; a plurality of normally open switches each adapted to be closed in response to a particular condition, such as deformation of the craft structure, crash and engine or propeller reaction; and means individually connecting in series each switch with which another of the switches in a manner whereby upon the closing of at least two switches energization of the electroresponsive means is effected.

A preferred embodiment of the invention has been chosen for purposes of illustration and description, and

2 is shown in the accompanying drawings, forming a part of the specification, wherein:

l is a schematic view of a portion of a system in accordance with the invention including a wiring diagram of the circuit utilized in connection with the systern.

Figs. 2 to 7 are simplified wire diagrams illustrating the arrangement of switches which are closed in response to particular conditions to effect energization of electroresponsive means in the event at least two of such switches are closed, the live portion of the diagram or the circuit established being shown in heavy lines and the remainder of the diagram being shown in lighter lines.

Referring to the drawings in detail and more particularly to Fig. 1 thereof, there is shown a fire preventing and extinguishing system for aircraft which, in general, comprises a plurality of fire preventing and/ or extinguishing devices for the right and left nacelles (only the devices for the right nacelle being shown), and a circuit for effecting actuation of the devices in response to particular conditions.

The fire preventing and/ or extinguishing devices shown here comprises a normally closed switch 10 adapted to be opened by a solenoid 11 to disconnect a generator 12 which supplies electrical energy to the circuit; two sources of coolant 14 and 15 adapted to be released by electrically initiated means 16 for destructing disc valves 17 confining the medium which is to be directed to the engine exhaust collector ring 18 to cool the same; a solenoid 19 for effecting closing of a normally open valve 26 in the oil line; a solenoid 21 for effecting closing of a normally open valve 22 located in the fuel line downstream of the engine carburetor; a solenoid 24 for effecting closing of a normally open valve 25 located in the fuel line upstream of the filter; a solenoid 26 for effecting opening of a normally closed valve 27 for controlling the release of fire extinguishing medium from its source 29; a solenoid 36 for opening a normally closed switch 31 to disconnect the ships battery 32 from the generator 12 which charges the same; and a time delay circuit breaker 34 for opening a normally closed switch 35 to disconnect the battery from the energy supply line 36 of the circuit. The circuit breaker, the solenoids and the disc valve destructor means are connected in and are operable by the circuit about to be described.

The control circuit for the devices just described comprises in general a plurality of condition responsive relays A, B, C and D, four being shown by Way of example, and left and right master relays L and R for effecting actuation of the devices in the left and light nacelles, respectively.

Insofar as the relays A, B, C and D are alike, each of these relays includes a coil 40, an armature 41, a switch 42 operated by the armature to maintain the coil energized, a condenser 44 shunted across the coil, a normaliy open condition responsive switch 45 adapted to close momentarily to effect energization of the coil, and a normally closed thermoresponsive switch 46 in series with the switch 42 which is adapted to be opened after being energized for a predetermined period of time to deenergize the relay coil.

By way of example, the condition responsive switches 45 of the relays A, B, C and D are adapted to be closed in response to impact or inertia, deformation of the wings, deformation of the belly, and propeller reaction, respectively. Since such switches and/or devices for operating the same are well known, illustration and description thereof are not deemed necessary.

The relays A, B, C and D further include an indicator and test lamp 47 and a manually operable single-pole double-throw switch 50 having a switch element normally 3 engaging a contact 51 to connect the lamp across the relay coil 49, whereby the lamp is illuminated when the coil is energized. In order to test the lamp, the switch element of the switch 50 is moved into engagement with a second contact 52 of this switch which is grounded, whereby the lamp is directly connected to the energy iine 36 and is illuminated. In addition, a normally closed manually operable switch 54 is provided in the energy line 36 at a point to cut out the relay coil 40 and the lamp upon opening the same.

The relays A, B, C and D, however, difier in the manner about to be described.

The relay A includes a single-pole single-throw switch 55 having first and second terminals 56 and 57, and a switch element 59 operable by the relay armature 41. This element is connected to the second terminal 57 and normally is out of engagement with a contact connected to the first terminal 56.

The relay B includes a single-pole single-throw switch 60 having first and second terminals 61 and 62, and a switch element 64 operable by the relay armature 42. This element is connected to the second terminal 62 and normally is out of engagement with a contact connected to the first terminal 61;

The relay C includes a single-pole single-throw switch 65 having first and second terminals 66 and 67, and a switch element 69 operable by the relay armature 41. This element is connected to the second terminal 67 and normally is out of engagement with a contact connected to the first terminal 66. The relay C further includes a single-pole double-throw switch 70 having first and second terminals 71 and 72, and a switch element 74 operable by the relay armature 41. This element normally is out of engagement with a contact connected to the first terminal 71 and is normally in engagement with a contact connected to the second terminal 72.

The relay D includes a single-pole single-throw switch 75 having first and second terminals 76 and 77, and a switch element 79 operable by the relay armature 41. This element is connected to the first terminal 76 and normally is out of engagement with a contact connected to the second terminal 77. The relay D further includes a single-pole double-throw switch 86 having first and second terminals 81 and $2, and a switch element 84 operable by the relay armature 41. This element normally is out of engagement with a contact connected to the first terminal 81 and is normally in engagement with a contact connected to the second terminal 82.

The master relay R includes a coil 85, an armature 86 and five normally open switches 87, 88, 89, 9t) and 91 for respectively controlling the energization of the generator cutout solenoid 11 and the valve destructor means 16, the oil line valve closing solenoid 19, the downstream fuel line valve closing solenoid 21, the upstream fuel line valve closing solenoid 24, and the fire extinguishing release valve opening solenoid 26.

The master relay L is substantially identical to the relay R, but, in addition, includes a normally open switch 92 for energizing the battery cutout solenoid 30 and the time delay circuit breaker 34.

The switches 87, 88, 89, 9t), 91 and 92 have one side connected to the energy line 36 which is in connection with one side of the battery 32, and have the other side connected to one terminal of the devices which are controlled thereby. The other terminals of these devices are grounded to complete circuits to the grounded side or" the battery.

The solenoids and the destructor means can also be energized at will directly from the energy line 36 by manually closing normally open switches 94 and 95 to selectively control the devices of the right and left nacelles, upon an indication that a fire has broken out in normal flight, Without disturbing the master relays and the controls therefor.

As previously indicated herein, the master relays R and L are to be energized when at least two of the condition responsive switches 45 are closed at the same time. This is achieved by electrically connecting the terminals and switch elements of the various switches operable by the relays A, B, C and D in the manner about to be described.

The energy line 36 has branches connected to the terminal 71 of switch 70 (relay C), the terminal 77 of switch 75 (relay D), and the terminal 82 of switch 8% (relay D). A conductor 96 connects the terminal 56 of switch (relay A), the terminal 61 of switch (relay B), the terminal 66 of switch (relay C), and the terminal 76 of switch 75 (relay D). A conductor 97 connects the terminal 57 of the switch 55 (relay A) and the switch element 34 of the switch 30 (relay D); and a conductor 98 connects the terminal 62 of switch 60 (relay 8) and the switch element 74 of the switch 76 (relay C). A conductor 99 is connected to one side of the master relay coils 85, and has branches connected to the terminal 67 of switch 65 (relay C), the terminal 72 of switch 79 (relay C) and the terminal 31 of switch 39 (relay D).

The manner in which a circuit is established for energizing the master relay coils 85 when two condition responsive switches 45 are closed is illustrated schematically in Figs. 2 to 7. in these views, a relay coil 85 is shown which could be associated with either of the master relays R or L, and a switch S is shown which is representative of the switches 87, 88, 89, 90, 91 and 92 controlled by the master relays. The circuit established from the battery 32 to the coil 85 is indicated in heavy lines, while the unafiected portions of the wiring diagram are in lighter lines.

In Fig. 2, the coil 85 is shown energized in response to the closing of the condition switches 45 associated with the relays A and B, whereby the normally open switches 55 and 60 are closed upon operation of these relays. Ac cordingly, current flows from the battery 32 through the energy line 36, terminal 82, switch element 84, conductor 97, terminal 57, switch element 59, terminal 56, conductor 96, terminal 61, switch element 64, terminal 62, condoctor 98, switch element 74, terminal 72 and conductor 99 to the coil 35, thus causing the switch S to be closed.

In Fig. 3, the coil 85 is shown energized in response to the closing of the condition switches 45 associated with the relays A and C, whereby the normally open switches 55 and 65 are closed and the switch is moved to its other position upon operation of these relays. Accordingly, current flows from the battery 32 through the energy line 36, terminal 82, switch element 84, conductor 97, terminal 57, switch element 59, terminal 56, conductor 96, terminal 66, switch element 69, terminal 67 and conductor 99 to the coil 85, thus causing the switch S to be closed.

In Fig. 4, the coil 85 is shown energized in response to the closing of the condition switches 45 associated with the relays A and D, whereby the normally open switches 55 and are closed and the switch 30 is moved to its other position upon operation of these relays. Accordingly, current flows from the battery 32 through the energy line 36, terminal 77, switch element 79, terminal 76, conductor 96, terminal 56, switch element 59, terminal 57, conductor 97, terminal 82, switch element 84, terminal 81 and conductor 99 to the coil 85, thus causing the switch S to be closed.

In Fig. 5, the coil is shown energized in response to the closing of the condition switches 45 associated with the relays B and C, whereby the normally open switches 69 and 65 are closed and the switch 70' is moved to its other position upon operation of these relays. Accordingly, current flows from the battery 32 through the energy line 36, terminal 71, switch element 74, conductor 93, terminal 62, switch element 64, terminal 61, conductor 96, terminal 66, switch element 69, terminal 67- and conductor 99 to the coil 85, thus causing the switch S to be closed.

In Fig. 6, the coil 85 is shown energized in response to the closing of the condition switches 45 associated with the relays B and D, whereby the normally open switches 60 and 75 are closed and the switch 80 is moved to its other position upon operation of these relays. Accord ingly, current flows from the battery 32 through the energy line 36, terminal 77, switch element 79, terminal 76, conductor 96, terminal 61, switch element 64, terminal 62, conductor 98, switch element 74, terminal 72 and conductor 99 to the coil 85, thus causing the switch S to be closed.

In Fig. 7, the coil 85 is shown energized in response to the closing of the condition switches 45 associated with the relays C and D, whereby the normally open switches 65 and 75 are closed and the switches 70 and 80 are moved to their other position upon operation of these relays. Accordingly, current flows from the battery 32 through the energy line 36, terminal 77, switch element 79, terminal 76, conductor 96, terminal 66, switch element 69, terminal 67 and conductor 99 to the coil 85, thus causing the switch S to be closed.

In operation, should any two condition switches be closed to establish the circuits just described in connection with Figs. 2 to 7, both master relays R and L are energized and the switches 87, 88, 89, 90, 91 and 92 are closed whereby the solenoids 11, 19, 21, 24 and 26 and the valve destructor means 16 are energized to put into operation the fire preventing and/ or extinguishing devices which they control, "and the solenoid 30 and the circuit breaker 34 are energized.

In the event that two condition switches close simultaneously only momentarily, that is, for an insufiicient time to completely energize the relay coils 40 which they control, the condensers 44 connected across these coils will be charged, and, upon discharging eifect energization of their coils to operate the armature 41 associated therewith, whereby the master relays are caused to be energized.

It has been found that the master relays R and L operate within about .02 of a second after closing of the condition switches 45, and that the fire preventing and/or extinguishing devices are rendered effective within about .04 of a second after closing of the switches 45. The battery solenoid 30 operates the switch 31 within about .04 of a second after closing of the switches 45 to deenergize the line 100 between the battery 32 and the generator 12. The time delay circuit breaker functions to open the switch 35 and deenergize the line 36 within about .1 of a second after closing of the switches 45, thus providing for the energization of the circuit for a sufficient duration to assure operation of the master relays and the devices controlled thereby but still deenergizing the circuit completely within a time before combustible fluids or vapors can be ignited by sparks or hot wires within the circuit.

Provision is made against false alarm indications and trouble, caused by circumstances other than the particular conditions sought to be detected, by the association of the lamp 47 and the switches 50 and 54 with the relays A, B, C and D. For example, in the event one of the condition switches 45 is closed or a short circuit develops temporarily while the craft is in normal flight and there is no apparent danger of crash or collision, the relay coil 40 actuates the armature 41 causing the relay switches including the holding switch 42 to be operated and at the same time the lamp 47 associated with such condition switch is illuminated indicating that there is trouble. The holding switch 42 maintains the relay coil 40 energized and causes current to pass through the heater 43 which in turn efiects actuation of the bimetallic switch element 48 of the thermoswitch 46, whereupon the switch 46 is opened within about ten seconds and the relay coil 40 is deenergized provided that the trouble condition has been corrected. When this occurs the lamp 47 is extinguished to indicate that the temporary trouble condition no longer exists (Fig. 1).

Should the trouble condition persist after about ten seconds have elapsed, the craft is inspected for trouble, and, if there is no danger at hand, the lamp can be extinguished manually by moving the switch element of the switch 50 into a neutral position between the contacts 51 and 52, or the relay in which the trouble exists can be temporarily disconnected from the energy line 36 by opening the switch 54.

In the event trouble develops in a second relay circuit, such relay can likewise be disconnected, and so forth for the third and fourth relay circuits, thereby leaving the system under manual control. This contingency is very unlikely, but, in any event, the system is safe-guarded against unintentional, unnecessary or premature operation by the simultaneous occurrence of two or more trouble conditions.

After a trouble condition has been indicated and the switch 54 has been opened, it can be determined from time to time whether or not the trouble still exists by closing the switch 54 momentarily while the switch element of the switch 50 engages the contact 51. If the trouble exists, the lamp 47 will be illuminated again.

The lamps 47 can be tested periodically to determine their working condition by causing the switch element 50 to engage the contact 52.

A further feature or" the circuit, in accordance with the invention, is that the switches 42 and 45 for effecting energization of the coils 40 of the rciays A, B, C and D are between the relay coils and the ground connection, instead of being between the coils and the battery con nection as is generally customary or prescribed. In this manner, if crash or collision occurs and the connections from the switches to the coils are cut or otherwise disrupted, such connections, upon coming in contact with sections of the craft to which the battery 32 is grounded, produce the same efiect attained by the closing of the switches 42 and 45, whereby the system will be operated even under such abnormal conditions.

While the circuit has been described in connection with four relays (A, B, C and D), it will be understood that any greater number of such relays associated with a condition switch may be utilized without departing from the present invention.

From the foregoing description, it will be seen that the present invention provides a relatively simple, practical, reliable and quick acting control circuit for fire extinguishing and/or preventing system of the type indicated herein, which circuit is safeguarded against false operation.

As various changes may be made in the form, construction and arrangement of the parts herein, without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.

We claim:

1. In an aircraft, a system for automatically initiating the operation of safety equipment such as fire-preventing or extinguishing equipment for the aircraft in the event of crash or impact, comprising normally inactive safety equipment including an electroresponsive device for rendering said equipment active; a circuit for initiating the operation of said electroresponsive device including a source of electrical energy and a normally open switch connected in series with said source and said device; elec troresponsive means having one terminal connected to one terminal of said source and arranged for effecting closing of said switch; a relay operable by said source including a normally open single-pole single-throw switch having first and second terminals; a second relay operable by said source including a normally open single-pole single-throw switch having first and second terminals; a

third relay operable by said source including a normally open single-pole single-throw switch having first, and sec ond terminals and including a single-pole double-throw switch having first and second terminals and a switch arm normally in electrical connection with said last mentioned second terminal; a fourth relay operable by said source including a normally open single-pole single-throw switch having first and second terminals and including a singlepole double-throw switch having first and second terminals and a switch arm normally in electrical connection with said last mentioned second terminal; a conductor electrically connecting said first terminals of all of said single-throw sw' ches; a conductor electrically connecting said second terminal of said switch of said first relay and said switch arm of said double-throw switch of said fourth relay; a conductor electrically connecting said second terminal of said switch of said second relay and said switch arm of said doublethrow switch of said third relay; a conductor electrically connecting said second terminal oi said single-throw switch of said third relay to said first terminal of said double-throw switch of said fourth relay, said second terminal of said double-throw switch of said third relay and the other terminal of said electroresponsive means, and a conductor'electrically connecting said second terminal of said single-throw switch of said fourth relay to said second terminal of said double-throw switch of said fourth relay, said first terminal of said double-throw switch of said third relay and the other terminal of said source, whereby actuation of at least two of said four relays is required to effect energization of said electroresponsive means.

2. A system according to claim 1, wherein means are provided for effecting energization of said relays to operate theswitch thereof automatically in response to a particular condition.

3. A system according to claim 2, wherein each of said relays includes a normally open switch adapted to be closed upon energization of said relays to maintain said relays energized.

4. A system according to claim 3, wherein a normally closed thermoresponsive time delay switch is connected in series with the respective coil and last mentioned switch of each of said relays, whereby, upon energization of said relays, said thermoswitches are energized and caused to open after a predetermined elapse of time.

5. A system according to claim 4, wherein a condenser is shunted across the respective coil of each of said relays.

References Cited in the file of this patent UNITED STATES PATENTS 1,516,646 Roseby Nov. 25, 1924 2,047,122 Brandenburger July 7, 1936 2,170,237 Farmer Aug. 22, 1939 2,539,206 Robinson Jan. 23, 1951 2,581,338 La Roza Ian. 8, 1952 2,594,520 Tiedman Apr. 29, 1952 2,683,194 Mathisen July 6, 1954 FOREIGN PATENTS 109,525 Australia Ian. 9, 1940 

